Playback is used to access data fraudulently through the unlawful copying of the prior content of a data management system. For example, if it is assumed that, at a time t0, a system S0 has read rights to a file F, that at the time t subsequent to t0, these rights are consumed with a content of said system equal to S, then playback allows fraudulent access to the read file F at the time t by copying the content of the system S0 in the system S to obtain a system containing S0 acknowledged as valid at the time t.
Conventionally, data in prior art systems is protected against playback by sending random events that change with every session, a time-stamp, or else, monotonic counters.
Sudden interruptions in service may impair the data contained in a physical medium for example when said data is read or written. These sudden interruptions in service are generally caused by the data management system being suddenly blacked out, mainly in the event of an electricity power cut or in the event of said system being inadvertently rebooted. Impairment to the written or read data may furthermore be caused by acts of aggression, when a malefactor intentionally alters the read or write behaviour in the data management system, or else, in the event of accidental errors occurring, in particular, following damage to the hard disk read-head or to the mechanism causing it to move.
Conventionally, the data in prior art systems is protected against sudden interruptions in service by providing for said data to be backed up and allowing the backed up data to be recovered. For example, when the data medium is a hard disk, this disk is mounted in a RAID (Redundant Array of Independent Disks) using one or more additional disks. The arrangement of disks in RAID 1 will be cited in particular.
However, to combine, on the one hand, data recovery further to impairments caused by sudden interruptions in service with, on the other hand, protection of said data against playback, is no easy matter. Indeed, in respect of data recovery, it is wished to retrieve data that has been subject to impairment, whereas, in preventing playback, the aim is to prevent any retrieval of said data. Combining a backup system for a partition containing data with protection for said partition against playback that includes monotonic counters therefore seems incompatible. In the opposite situation, recovering an old saved partition would be in contradiction to the anti-playback protection system since it would use a prior value of the monotonic counter.
Given the prior art disclosed above, a problem to which the invention offers a solution is the implementation of a system and a method for making data secure against, on the one hand, playback and, on the other hand, data changes due in particular to a last interruption in service.